Question 60

If 12, x, 8 and 14 are in proportion, then what is the mean proportional between (x - 12) and (x + 4)?

Solution

12, x, 8 and 14 are in proportion,

=> $$\frac{12}{x}=\frac{8}{14}$$

=> $$8x=14\times12$$

=> $$x=7\times3=21$$

Thus, mean proportional between $$(x-12)=21-12=9$$ and $$(x+4)=21+4=25$$ is

= $$\sqrt{21\times9}=\sqrt{225}=15$$

=> Ans - (D)

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